This commercially available sensor was the product of work from many
at OSU, Mike Thralls with the Oklahoma Conservation Commission, the Soil
Fertility Research and Education Advisory Board with oversight from Joe
Neal Hampton, and the Oklahoma Agricultural Experiment Station.

1) The sensor comes pre-calibrated to a Greenseeker
sensor. (the manual below would indirectly suggest that the sensor might
not be calibrated)
2) The sensor can be calibrated to an “NDVI “ sensor
(not just a Greenseeker)
3) The existing “Greenseeker calibration must be turned
to FALSE (G, F) before re-calibrating

One thing that needs to be enforced is charging the battery of the pocket
sensor every night.
Also, before calibration, the sensors need to be fully charged.
This will ensure the sensor is operating at it's best.

Charging:

·Attach the provided USB
cable attachment to the front side of the pocket sensor, then plug in the
USB cable directly into a USB port on a computer.Charge for 3-4 hours.

·Battery life is
approximately 6-10 hours, depending on operation

·A “batt” symbol will
appear in the upper left-hand corner of the LCD screen if a low-battery
condition occurs.

Operation

·Care must be taken to
keep the pocket sensor level while sensing, at a height of 24”
to 30” (60-75 cm) above the crop canopy.The target is circular with a dimension shown in Figure 1.

·To operate, place the
pocket sensor at the appropriate height above the canopy, thenpush and hold the red button.

·While holding the red
button, walk slowly down the treatment (or strip) that you want to sense.You will notice the NDVI value being displayed on the screen
changing once per second during operation.

·When you are done
sensing, release the red button and note the last number displayed on the
screen.This is the average
of all readings that were taken while the button was depressed.

·Write down or remember
this number quickly, because it will only be displayed for a few seconds
before it disappears.Ensuing
readings once the red button is pressed again start anew.

·The pocket sensor does
not have the capability of storing data, so you must record the NDVI
values that you need after each operation.

Figure 1.Target dimension for different sensing distances

Storage

·Store in the cardboard
box provided.Be very
cautious about placing the pocket sensor face down on any
surface, as this could scratch the LED lenses.

Error Messages

·An error message may be
displayed on the screen if something is wrong.The following messages may appear, with the correct description:

oE01 – calculated NDVI
value is less than 0, which is invalid

oE02 – calculated NDVI
value is greater than 1, which is invalid

Hours of Operation

·The pocket sensor
should provide the same readings day or night, as this is an active
sensor.You will not want to
use the sensor if it is raining or in extreme heat or cold.

----------------------------------------------------------

This should already have been accomplished, but if not, re-calibration
procedures follow

Calibration Procedure
for Pocket Sensor:

1.
Before the Pocket Sensor can be calibrated, any existing calibration must
be set to 0.Do this by:

A.Plug the pocket sensor
into a USB port on a computer, and follow the Installation instructions to
download the driver onto the pocket sensor.The correct driver to download is the Silicon Labs CP210x USB to
UART Bridge.This can be
downloaded from
http://www.silabs.com/products/mcu/pages/usbtouartbridgevcpdrivers.aspx
and select the correct computer operating system.

J.
In the terminal program select “Disconnect” the sensor has now been set to
its original calibration, and can be calibrate with the GreenSeeker.

2.Calibration must be
done with a Greenseeker.Take
at least 70-100 readings with both the Pocket Sensor and the Greenseeker
over different types of surfaces (bare soil, different shades of
vegetation, etc.).

Note:Make sure that the areas sensed by
both the Greenseeker and Pocketsensor are exactly the same.Pick an area about 24” (60 cm) square, that is flat and
homogenous.

3.Enter the NDVI values
of both Greenseeker and Pocket sensor into Microsoft Excel.Place the Pocket sensor values in the left column (for the
independent, x-axis) and the Greenseeker values in the right column (for
the dependent, y-axis).

4.Plot these values as a
scatter plot.Make sure that
Pocket sensor values are on the x-axis and Greenseeker values are on the
y-axis.

5.On the scatter plot,
right-click on the mouse over the points, and select “Add Trendline”.

6.On the Trendline menu,
select “Polynomial” on the Regression Type, and “2” on the Order.Also check the boxes for “Display Equation on chart” and “Display
R-squared value on chart”.

7.The Excel chart will
now display the calibration equation that needs to be entered into the
pocket sensor for calibration.

Entering the
Calibration Equation into the Pocket Sensor:

1.
Connect the Pocket Sensor to the computer and open the terminal program as
outlined in previous section.

2.
Press “p” to print calibration numbers and menu
options.

--Caution!!!DO NOT press “f” while on the menu page, as this will restore
the memory to the default settings, and will render the sensor unusable
until reset by an OSU Engineer!!!!

3.Press “g” to set the
coefficients for the calibration equation.

4.Once “g” is entered
into the terminal, enter the values for the calibration equation.

5.Press “t” for True when
it states “Enter
CalNum.u8Flag.(T/F)……”

6.The formula is in the
form of:y = Ax² + Bx + C.The values A, B, and C will then be entered into the terminal
program:-- “Enter CalNum.fpA….”Enter value for A, then press Enter-- “Enter
CalNum.fpB….”
Enter value for B, then press Enter-- “Enter
CalNum.fpC….”
Enter value for C, then press Enter

Be careful to note the sign (+ or -) for the Ax2 value.

7.The Pocket Sensor is
now calibrated and ready for use.Press “Disconnect” in the upper-left corner of screen to disconnect
the device.

Note:While the Pocket sensor is plugged into the terminal program, it is
possible to capture individual sensor readings.To do this, plug the sensor into the computer and connect to the
terminal program, and press “p” to display the sensor values.

Experiences with the
PocketSensor:

During calibration of the Pocket sensor at the CIMMYT Research
Station in El Batan, Mexico, some considerations were:Wheat is planted on raised beds, and at the time of sensing the
wheat was headed out (Reproductive Stage).The height of the wheat and the distance between beds allowed the
GreenSeeker to read soil background while the Pocket sensor was only able
to read the rows of wheat, the soil was to far away.It is imperative that both the GreenSeeker footprint and Pocket
sensor be over the same targeted area to get an accurate calibration.Note:This may not be an issue when the wheat is vegetative and the
soil is still within range of the Pocket sensor.